This fixes the rendering of the scan visor in Metroid Prime 2: Echoes,
as seen in https://fifoci.dolphin-emu.org/dff/mp2-scanner/
The alpha channel was off-by-one on Ivy Bridge due to the rounding
after multiplication with colmat. This commit removes this matrix
altogether in most cases, making them simple GLSL swizzles.
They are already disabled when the libraries can’t be found, this only
helps people who want to build without them despite having them
installed, for example to provide a package to someone else.
Emmanuel Gil Peyrot